Well's Criteria for Pulmonary Embolism

The Wells' Criteria risks stratifies for pulmonary embolism (PE). The criteria estimate pre-test probability and guides testing required for diagnosing a PE. The score is often used in conjunction with d-dimer testing. The Wells' Criteria has be validated in both inpatient and emergency department settings.

The intent of the Wells' score was to determine if the patient was low risk enough to rule out testing with a d-dimer. In clinical practice, the Well's score is often used to predict who is low-risk and then apply the PERC rule to stop workup for PE. 

Well's Criteria is not meant to diagnose Pulmonary Embolism (PE). The scoring system cannot completely rule out PE in patients with a low probability score or confirm PE with a high probability score. A thorough history and physical must be completed first with findings that suggest venous thromboembolism (VTE) as a diagnostic possibility. Second to a history and physical is application of the Wells' Criteria. A common mistake made is applying the Wells' Criteria or ordering the d-dimer as the first order or operations. For example, by applying the model to or ordering a d-dimer on all patients with chest pain or shortness of breath or to all patients with leg pain or swelling without first obtaining a history and physical exam. A d-dimer can be falsely positive for many patients with non-VTE. 

The score can guide your workup by 

• Predicting pre-test probability of PE.
• Guide appropriate testing to rule out the diagnosis, such as d-dimer or CT angiogram.
• Inform interpretation of subsequent diagnostic tests.
• Reduce the need for invasive testing.
• There must first be clinical suspicion for PE in the patient, such as presentation of symptoms (chest pain, shortness of breath, etc.).

The Wells' Criteria can be applied in two ways, three tier model or the two tier model. The two tier model is preferred and supported by the American College of Emergency Physicians (ACEP) 2011 clinical policy of PE. The two tier model uses only the high sensitivity d-dimer and more conservative risk stratification. It is thought that "intermediate" risk patients, such as the three tier model, may be at too high risk to be evaluated without further risk stratification.

Wells' Criteria

Three Tier Model

Low Risk: 1.3% incidence of PE in the ED population (<2 points)

• An alternative is to consider applying the PERC rule-out criteria to stop workup for PE
• Consider d-dimer testing to rule out pulmonary embolism
  • If the dimer is negative consider stopping the workup
  • If the dimer is positive consider CTA

Moderate Risk: 16.2% incidence of PE in the ED population (2-6 points)

• Consider high sensitivity d-dimer testing or CTA
  • If the dimer is negative consider stopping the workup
  • If the dimer is positive consider CTA

High risk: 40.6% incidence of PE in an ED population (> 6 points)

• Due to higher risk, consider CTA
  • D-dimer testing is not recommended.

Two Tier Model

PE Unlikely: 3% incidence of PE (0-4 points)

• Consider high sensitivity d-dimer testing 
  • If the dimer is negative consider stopping the workup
  • If the dimer is positive consider CTA

PE Likely: 28% incidence of PE (> 4 points)

• Due to higher risk, consider CTA testing.

Well's Criteria is not meant to diagnose Pulmonary Embolism (PE). 

• The scoring system cannot completely rule our PE in patients with a low probability score or confirm PE with a high probability score. 

A d-dimer can be falsely positive for many patients with non-VTE.

• There must first be clinical suspicion for PE in the patient, such as presentation of symptoms (chest pain, shortness of breath, etc.). 
• A thorough history and physical must be completed first with findings that suggest venous thromboembolism (VTE) as a diagnostic possibility. 
• Second to a history and physical is application of the Wells' Criteria. 
• A common mistake made is applying the Wells' Criteria or ordering the d-dimer as the first order or operations. For example, by applying the model to or ordering a d-dimer on all patients with chest pain or shortness of breath or to all patients with leg pain or swelling without first obtaining a history and physical exam. 

The score can guide your workup by 

• Predicting pre-test probability of PE.
• Guide appropriate testing to rule out the diagnosis, such as d-dimer or CT angiogram.
• Inform interpretation of subsequent diagnostic tests.
• Reduce the need for invasive testing.